Ip based lawful interception at the source

Abstract

A system and method for lawful intercept of call content incorporates a control element receiving subscriber information as a lawful intercept target and issuing a media forking command to a media transfer element transmitting RTP data. The media transfer element receives the media forking command and provides duplicates of RTP data packets associated with the subscriber transmitted through the media transfer element for transmission to a delivery function. The media forking command is an attribute in an SDP and includes definition of IP addresses for at least one delivery function. An acknowledgement of the forking command from the media transfer element to the control element is provided.

1 . A method for lawful intercept of call content comprising the steps of:
 receiving subscriber information as a lawful intercept target;   issuing a media forking command to a media transfer element transmitting RTP data;   receiving the media forking command in the media transfer element and   providing duplicates of RTP data packets associated with the subscriber transmitted through the media transfer element for transmission to a delivery function.   
   
   
       2 . A method as defined in  claim 1  wherein the media forking command includes definition of IP addresses for at least one delivery function. 
   
   
       3 . A method as defined in  claim 1  further comprising the step of providing an acknowledgement of the forking command from the media transfer element. 
   
   
       4 . A method as defined in  claim 1  wherein the media forking command comprises an attribute in a SDP. 
   
   
       5 . A method as defined in  claim 3  wherein the acknowledgement comprises an attribute in a local SDP. 
   
   
       6 . A method as defined in  claim 2  wherein the forking command includes multiple delivery function IP addresses to support forwarded call interception. 
   
   
       7 . A method as defined in  claim 4  wherein the media the media forking command is an attribute having a format for
 a=Name:<incoming_destination_>;<outgoing_destination_list>.   
   
   
       8 . A method as defined in  claim 7  wherein the incoming destination list and outgoing destination list are in the format destination_list=ip:port,ip:port, . . . 
   
   
       9 . A method as defined in  claim 1  wherein the media transfer element is a BSC and an MSC receives the lawful intercept target subscribe information and issues the media forking command. 
   
   
       10 . A method as defined in  claim 9  wherein the MSC and BSC employ MEGACO and the media forking command is an attribute in the Local and Remote session description protocols for incoming and outgoing media streams, respectively, sent by the MSC as soon as LI-Information becomes available and having a format of a=attributename:<destination_list> 
   
   
       11 . A method as defined in  claim 10  wherein the destination list in the format for incoming and outgoing media streams are in the format destination_list=ip:port,ip:port, . . . 
   
   
       12 . A method as defined in  claim 9  wherein the MSC and BSC employ MGCP and the media forking command is an attribute with both the incoming and outgoing media stream forks specified within the Remote SDP. 
   
   
       13 . A method as defined in  claim 12  wherein the attribute format is a=Attributename:incomingipaddress:port,incomingipaddress:port, . . . ;outgoingipaddre ss:port,outgoing address:port, . . . 
   
   
       14 . A system for lawful intercept of call content comprising:
 a control element for receiving subscriber information as a lawful intercept target, said control element having means for issuing a media forking command;   a media transfer element transmitting RTP data and having
 means for receiving the media forking command and 
 means for providing duplicates of RTP data packets associated with the subscriber transmitted through the media transfer element for transmission to a delivery function.